一个方便的素催化 [4 + 2] 取消:合成高度功能化的四胺酸
Xue-Feng Zhu1, Jie Lan, Ohyun Kwon
1Department of Chemistry, University of California, Los Angeles, California 90095-1569, USA.
Journal of the American Chemical Society
|April 17, 2003
概括
一种新的素催化废除反应有效地合成了使用乙烯-2-甲基-2,3-二烯酸作为1,4-双极合成子的替代四二烯酸. 这种方法提供了优异的产量,区域选择性和多重选择性,用于多种类型的氨酸衍生物.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
- 催化剂是一种催化剂.
背景情况:
- 1,4-双极合成子是有机合成中有价值的构建块.
- 在药品和天然产品中,四胺基基架很常见.
- 开发高效的催化方法来合成异环非常重要.
研究的目的:
- 为了开发一种新的 [4 + 2] 解消反应,用于四二胺合成.
- 为了利用乙基2-甲基-2,3-丁酸作为一种新的1,4-双极合成.
- 探索已开发的注销的范围和立体选择性.
主要方法:
- 乙基2-甲基-2,3-丁酸盐与N-托西林胺的反应.
- 使用有机氨酸催化剂进行 [4 + 2] 取消.
- 使用替代乙基2- ((替代-甲基) -2,3-丁酸盐来扩大范围.
主要成果:
- 对于乙烯6替代-1-(4-托西尔) -1,2,5,6-四-二烯-3-碳酸盐,获得了优异的产量和完全的区域选择性.
- 反应范围的扩大产生了乙2,6-cis-异位-1-(4-tosiyl) -1,2,5,6-四-二烯-3-碳酸盐.
- 在脱位产品的合成中观察到高的二选择性.
结论:
- 已经建立了一个新的,高效的素催化 [4 + 2] 废除反应.
- 乙基2-甲基-2,3-丁酸盐作为一个有效的1,4-双极合成为四二胺合成.
- 这种反应提供了一条通往具有高度替代性四胺的多功能途径,具有受控立体化学反应.
相关概念视频
Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
Acid Halides to Carboxylic Acids: Hydrolysis
Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
Acid Halides to Esters: Alcoholysis
Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...


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